Sound-absorbing wall or ceiling.



W. C. SABINE.

SOUND ABSORBING WALL 0R CEILING.

APPLICATON FILED NOV. 29, |915.

5 vwmdoz UNTE STATES PATENT OFFICE.

WALLACE C. SABINE, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO H. W. JOHNS- MANVILLE COMPANY, A CORPORATION OF NEW YORK.

SOUND-ABSORBING WALL OR CEILING.

Application led November 29, 1915.

To all 'whom it may concern:

Be it known that l, WALLACE C. SABINE, a citizen of the United States of America, residing at Boston, county of Suffolk. State of Massachusetts, have invented certain new and useful Improvements in Sound-Absorbing \"i7alls or Ceilings, of which the following is a. specification.

My invention relates generally to the prevention or correction of a certain class of acoustical difliculties arising in auditoriums, lecture rooms, oilices and the like and due to excessive reverberation, echo, and injurious focusing of sound and similar causes.

More specifically my invention is designed to produce a type of wall or ceiling surfacing or covering which shall be efficient in the absorption and transmission of sound and also hygienic in character.

In some aspects the present invention is an improvement on that disclosed in U. S. Patent No. 1,119,543 granted December 1, 1914, to Rafael Guastavino and myself as joint inventors of an improved Wall or ceiling for auditoriums and the like, having in combination a supporting masonry struc- 're and attached thereto an exposed inner ver of linished masonry, sponge-like in ructure, the latter having pores which have .gid walls and are inter-communicating throughout the mass and openly penetrate the exposed finished surface, the said pores being of such proportional and varia-nt dimensions that said inner -masonry material possemes the property of absorbing in excess of ten per centum of sounds lying in pitch between middle C and a third octave-above middle C. This masonry-material is designed to take the place of felt which is in large use today in acoustical correction in consequence of my investigations. Such masonry material has the advantage of being durable, vermin free, -and fireproof. It

is, however, because of its porosity, not eptirely hygienic and therefore not acceptable as an exposed surface under many conditions.

It is the object of this invention to provide walls and ceilings which, while retaining the many advantages of sound absorbing masonry, are hygienic and nonporous in their outer exposed surface. This result is accomplished by combining an outer impervious, non-porous but flexible membrane with an under structure of porous Specification of Letters Patent.

Patented. Nov. 21, 1916.

Seria1No. 64,150.

made of muslin of other fabric stretched bctween battons and then sized. lt thusloses 'l its p orosity but remains flexible. Or the muslm may be rendered impervious by the application thereto of a covering layer of' paper. Membranes prepared in different ways havediii'erent weights and dilferent tensions, these properties having perceptible eiects on the acoustical value of the resulting combination, as will be ,explained later. The sizing ofthe stretched muslin or pasting of paper thereon tends to shrink the fabric and increase the tension of the sheet.

A porous covering transmits the sound from the room to the sound absorbing ma. sonry material beneath, partially by direct air communication through'the open pores, and partially by itself yielding in vibration, and inthis process of transmission it itself acts as a sound absorbent. 'The impervious non-porous membrane herein described transmits the sound to the sound absorbing masonry beneath'only by yielding in vibration. The present invention, therefore, in anA endeavor to secure a smooth hygienic surface, loses somewhat' in acoustical efficiency under certain conditions. Properly executed, however, with a suiiiciently light membrane the loss of acoustical eiiciency is not great and under certain conditions, .particularly in school rooms and the like,

hygienic considerations more than compensate for this slight loss. While there is this loss ini 'aggregate sound absorbing power considering sounds of all audible pitch, so far as sounds of the ordinary range of pitch of the speaking voice are concerned, the capacity of resonance to such sounds in the stretched membrane can be made to heighten the sound absorbing action of the complete structure. Byresonance, in the sense here used, is meant the eapacity'for sympathetic vibration. These sympathetic and impressed vibrations act to partly absorb and partly transmit the sound Waves lto thesound absorbing masonry material beneath. The absorbing power ofthe combination, membrane and masonry beneath, is thus concentrated over certain ranges of pitch. If the weight and tension of the membrane are so adjusted that this concentration of absorbingT power is in thc` middle register and the innruuliatcly upper register, the vital range ol pitch` lln result is positively advantageous l'or all practical purposes in reducing the cello and rcvcrlafralions of ordinary speech` own though lluecho and roverl'ieration cll'ects may not be as greatly reduced for very high pitched notes.

,\ci'.:ordiugly the invention primarily consists in a porous artificial masonry material eapabhl oi" absorbing sound to a` high degree and of an impervious membrane stretched freely in front of it and capable of transmitting by ils yielding in vibration a consideralilc portion of the sound to the ma som-y beneath.

The best ,forni of construction at present lrnon'n to me embodying my invention is .shown in ilu accompanying drawings in \\'liich--- l Figure l a cross section of a wall treated in accordance with one manner of applying my invention, and ,Fig 2 is a. similar View showing a wall treated in accordance with another manner of applying my invention.

Throughout the drawings like reference characters indicate like parts.

l, is the main wall structure or backing, which may be of any ordinary building material giving the desired strength and general structural qualities.

E, 2, are sections or panels of porous, sound absorl inf 7 masonrymaterial such as is disclosed in Patent No. 1.119543 before referred to, which are set in cement 3. Over the surface so formed is stretched the nonporous sound absorbing membrane 4, such as sized muslin which may be fastened to battens 5, 5, or otherwise secured to the exterior of the masonry and which forms the interior surface of the room exposed to view by the occupants. The membrane 4, is stretched by the act of attachment or by subsequent treatment with size suflicientl'y to secure the desired degree of resonance to transmit sounds in the middle register, and is preferably parallel tothe main Wall surface leaving a. narroaT air space between the masonry material and the back of the membrane.

ln Fig. 2 the panels 2, 2, of porous masonry material are fastened to the Wall l, in any convenient manner, as by ap lication of a plaster-like layer thereof, and the membrane impervious and non-absorbent of moisture, dust and germs fastened to battens 5, 5, is composed of a sheet of muslin 6, ,or other light textile fabric to the face of which is 'pasted or otherwise attached sheets of paper 7.

In operation the sound waves in or near the middle register striking the stretched men'ibranc 1,1-, or 7, are largely transmitted thcrctl'irough by its yieldingin vibration, and are absorbed by the porous masonry material beneath` The porous masonry shown in Fig. 2 may be composed of a mixture of coarse sand, or broken stone, having all particles of substan tially the same size, and mixed with a small portion of Portland cement, say one third part by weight, and applied with a trowel. Ilhe small quantity of cement causes the particles of mineral aggregate to adhere one to another at their points of contact leaving spaces between.

The advantages of a wall or ceiling constructed in accordance with this invention are that it will be sufficiently absorbent to sound to have high corrective acoustical value in auditoriums and thelile, and at the same time have the hygienic and decorative quality of an impervious surface in the outer membrane and the durable, vermin-proof and incombustible character of masonry in the inner layer. i

Various changes could be made in the de tails of thepreferred construction herein shown and described without departing from the substance of the invention so long as the principle of arrangement and operation of parts above set out, is retained.

Having describcdmy invention, I claim:

1. A sound absorbing, hygienic and decorative surfacing for walls and ceilings, comprising in combination a porous, sound absox-hing layer of masonry material and a. relatively impervious non-porous elastic membrane composed of sheets of textile mf terial treated with size aHiXed theret stretched under tension in front of the fir. mentioned layer and separated therefrom by an intervening air space.

2. A sound absorbing, hygienic and decorative surfacing for Walls and ceilings, comprising in combination a porous, sound absorbing layerof masonry material, a relatively impervious, non-porous elastic membrane stretched in front of the-first mentioned layer under a tension sufficient to render it resonant to sounds in the middle and immediately upper registers and separated therefrom by an intervening air space anda series of Widely spaced supports projecting slightly beyond Athe outer surface of the porous masonry, to which supports the stretched membrane is attached.

WALLACE C. SABINE.

Witnesses i ANNA C. PARKER,

BENJAMIN 1. ELLIS. 

